Electromagnetically Driven Valve

ABSTRACT

An electromagnetically driven valve includes a drive valve that has a stem; an upper disk and a lower disk each of which has an arm portion, and each of which extends from a first end that is movably connected to the stem toward a second end that is movably supported by a disk supporting base; and an electromagnet. The electromagnet includes a core that is provided so as to face the arm portion, and a coil that is wound around the core. The electromagnet forms a magnetic circuit that passes through the core and the arm portion when an electric current is applied to the coil. The electromagnetically driven valve further includes a permanent magnet which has a magnetic axis along the magnetic circuit, and which is provided so as to act on a magnetic flux that flows through the magnetic circuit.

INCORPORATION BY REFERENCE

This is a 371 national phase application of PCT/IB2005/002503 filed 24Aug. 2005, claiming priority to Japanese Patent Application No.2004-251288 filed 31 Aug. 2004, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to an electromagnetically driven valve.More specifically, the invention relates to a rotary driven typeelectromagnetically driven valve used for an internal combustion engine.

2. Description of the Related Art

A conventional electromagnetically driven valve is disclosed in, forexample, Japanese Patent Application Publication No. 11-350929 A.Japanese Patent Application Publication No. 11-350929 A discloses aso-called parallel driven type electromagnetically driven valve intendedfor reliably attracting an armature to an electromagnet and realizinglow electric power consumption. The electromagnetically driven valvedisclosed in Japanese Patent Application Publication No. 11-350929 Aincludes a valve stem formed integrally with a valve element.

The valve stem is provided with a collar-shaped armature that extends inthe radius direction of the valve stem. A first electromagnet and asecond electromagnet are arranged with the armature interposedtherebetween. The electromagnetically driven valve further includes alower spring that applies a force to the valve element in the directionin which the valve is closed, and an upper spring that applies a forceto the valve element in the direction in which the valve is opened. Thelower spring and the upper spring are provided in series in the axialdirection of the valve stem. In the parallel driven typeelectromagnetically driven valve, an electromagnetic force generated bythe first electromagnet and the second electromagnet, and an elasticforce of the lower spring and the upper spring are directly applied tothe valve stem, whereby the valve stem reciprocates between the valveopening position and the valve closing position. An assist magnet forgenerating a large amount of electromagnetic force is provided in a coreforming the first electromagnet and the second electromagnet.

Japanese Patent Application Publication No. 04-276106 A discloses anelectromagnetically driven valve intended for efficiently driving anelectromagnetic valve. The electromagnetically driven valve disclosed inJapanese Patent Application Publication No. 04-276106 A is a paralleldriven type electromagnetically driven valve, as in the case of theelectromagnetically driven valve disclosed in Japanese PatentApplication Publication No. 11-350929 A. The electromagnetically drivenvalve includes a valve mechanism which drives an electromagnetic valveby using an electromagnetic force. A permanent magnet portion isprovided in a yoke forming the valve mechanism.

In the parallel driven type electromagnetically driven valve disclosedin Japanese Patent Application Publication No. 11-350929 A, a clearanceis formed between the first electromagnet and the second electromagnet.The armature reciprocates in the clearance while being alternatelyattracted to the first electromagnet and the second electromagnet. Thearmature and each of the first electromagnet and the secondelectromagnet are uniformly apart from each other while the distancetherebetween uniformly changes, except for the state where the valvestem is at one of the valve opening position and the valve closingposition. However, an electromagnetic force acts at a higher degree at aposition at which the distance from the electromagnet is shorter.Therefore, the electromagnetically driven valve disclosed in JapanesePatent Application Publication No. 11-350929 A has a problem that asufficiently large amount of electromagnetic force cannot be applied tothe armature, and, therefore, a large amount of driving force cannot beobtained. Such a problem also occurs in the parallel driven typeelectromagnetically driven valve disclosed in Japanese PatentApplication Publication No. 04-276106 A.

Document FR 2 792 451 discloses an electromagnetic drive mechanism,wherein the electromagnetic drive mechanism has a flexible returnsection to move a valve between an open and closed position. Theflexible return is made up of tongue sections pivoting about an axiswhich act on the valve spoke transforming movements to the valvemovement plane.

Further, document EP 1 010 866 A2 discloses an electromagnetic actuatingsystem having a valve member. The electromagnetic actuating systemincludes an armature which moves with the valve member, an electromagnetwhich attracts the armature in a direction of movement of the valvemember by being supplied with a current, and a spring which presses thearmature away from the electromagnet. A permanent magnet which can exerta magnetic attracting force between the armature and the electromagnetis provided. A current controller supplies a release current to theelectromagnet so that magnetic flux is generated in a direction oppositeto a direction of magnetic flux generated by the permanent magnet whenthe armature is released from the electromagnet. The valve memberfunctions as an intake valve or an exhaust valve of an internalcombustion engine, and the current controller controls an amount of saidrelease current in accordance with an operating state of the internalcombustion engine.

Finally, document DE 198 24 537 A1 discloses an electromagneticallydriven device having a valve stem and that reciprocates in a directionin which the valve stem extends. Further, an oscillating member havingan arm portion made of magnetic material extends from a first end and ismovably supported by a supporting member. The arm is oscillated by meansof an electromagnet that includes a core and a coil and forms a magneticcircuit.

SUMMARY OF THE INVENTION

The invention is made in light of the above-mentioned circumstances. Itis, therefore, an object of the invention to provide anelectromagnetically driven valve in which a sufficiently large amount ofdriving force can be obtained.

According to an aspect of the invention, there is provided anelectromagnetically driven valve including a drive valve which has avalve stem; two oscillation members being formed of a first oscillationmember and a second oscillation member, which have an arm portion madeof magnetic material, and which extends from a first end that is movablyconnected to the valve stem toward a second end that is movablysupported by a supporting member, respectively; and an electromagnet.The electromagnet includes a core that is provided so as to face the armportion, and a coil that is wound around the core. The electromagnetforms two magnetic circuits which pass through the core and the armportions when an electric current is applied to the coil for applyingmagnetism to the two oscillation members, respectively. Theelectromagnetically driven valve further includes a permanent magnetwhich has a magnetic axis along the magnetic circuits, and which isprovided so as to act on a magnetic flux that flows through the magneticcircuits. The permanent magnet is disposed so as to balance out themagnetic flux that flows through the magnetic circuit acting on one ofthe two oscillation members, and to increase the magnetic flux thatflows through the magnetic circuit acting on the other oscillationmember. The oscillation members are oscillated by using the second endas a supporting point due to an electromagnetic force applied from theelectromagnet. An oscillation motion of the oscillation member istransmitted to the drive valve via the first end, whereby the drivevalve reciprocates in the direction in which the valve stem extends.

According to another aspect of the invention, there is provided acontrol method for an electromagnetically driven valve including a drivevalve which has a valve stem and which reciprocates in a direction inwhich the valve stem extends; two oscillation members being formed of afirst oscillation member and a second oscillation member which aremovably connected to the valve stem; and an electromagnet which formstwo magnetic circuits between the electromagnet and the oscillationmembers for applying magnetism to the two oscillation members,respectively, wherein the permanent magnet is disposed so as to balanceout the magnetic flux that flows through the magnetic circuit acting onone of the two oscillation members, and to increase the magnetic fluxthat flows through the magnetic circuit acting on the other oscillationmember. The control method includes a first step in which a supply of anelectric current to the electromagnet is stopped, whereby theoscillation member, which is at a first position at which theoscillation members have been oscillated as much as possible so that thedrive valve is moved in a first direction, are started to be oscillatedtoward a second position at which the oscillation members are to beoscillated as much as possible so that the drive valve is moved in asecond direction that is opposite to the first direction; and a secondstep which is performed after the first step is completed, and in whichthe supply of the electric current to the electromagnet is startedbefore the oscillation member reaches a center position that is amidpoint between the first position and the second position. In thiscase, the first position may be a position at which the oscillationmember has been oscillated as much as possible so that the drive valveis opened, and the second position may be a position at which theoscillation member has been oscillated as much as possible so that thedrive valve is closed. Alternatively, the first position may be aposition at which the oscillation member has been oscillated as much aspossible so that the drive valve is closed, and the second position maybe a position at which the oscillation member has been oscillated asmuch as possible so that the drive valve is opened.

With the electromagnetically driven valve thus configured, when thedirection in which the magnetic flux flows in the permanent magnetmatches the direction in which the magnetic flux flows through themagnetic circuit, the strength of the magnetic flux flowing through themagnetic circuit is increased. On the other hand, when the direction inwhich the magnetic flux flows in the permanent magnet is opposite to thedirection in which the magnetic flux flows through the magnetic circuit,the strength of the magnetic flux flowing through the magnetic circuitis decreased. Accordingly, appropriately selecting the direction of anelectric current applied to the coil makes it possible to control theamount of electromagnetic force applied to the oscillation member sothat an oscillation motion of the oscillation member is promoted. Inaddition, in the invention, a method in which the drive valve isreciprocated due to the oscillation motion of the oscillation member isused as the method for driving the electromagnetically driven valve. Inthis case, the distance between the arm portion and the electromagnet ata position near the second end movably supported by the supportingmember is always shorter than the distance between the arm portion andthe electromagnet at a position near the first end movably connected tothe valve stem, regardless of the oscillation position of theoscillation member. Accordingly, a larger amount of electromagneticforce can be applied to the oscillation member. It is, therefore,possible to obtain a sufficiently large amount of driving force byproviding the permanent magnet in the rotary driven typeelectromagnetically driven valve.

As mentioned above, when the direction in which the magnetic flux flowsin the permanent magnet matches the direction in which the magnetic fluxflows through the magnetic circuit, the strength of the magnetic fluxflowing through the magnetic circuit is increased. On the other hand,when the direction in which the magnetic flux flows in the permanentmagnet is opposite to the direction in which the magnetic flux flowsthrough the magnetic circuit, the strength of the magnetic flux flowingthrough the magnetic circuit is decreased. Accordingly, it is possibleto start the supply of electric current to the electromagnet before theoscillation member reaches the center position while reciprocatingbetween the first position and the second position.

The permanent magnet may be provided in the core.

With the electromagnetically driven valve thus configured, it ispossible to cause the magnetic flux formed in the permanent magnet toact on the magnetic flux flowing through the magnetic circuit moreeffectively.

The permanent magnet may be provided between the core and the coil.

With the electromagnetically driven valve thus configured, it ispossible to avoid the situation where the core needs to be divided intotwo areas in order to provide the permanent magnet. As a result, thestructure of the electromagnet can be simplified.

The permanent magnet may be embedded in the core, and the core may bedivided into two areas by the permanent magnet on the magnetic circuit.

With the electromagnetically driven valve thus configured, it ispossible to cause the magnetic flux flowing through the magnetic circuitto pass through the permanent magnet reliably. It is, therefore,possible to cause the magnetic flux formed in the permanent magnet toact on the magnetic flux flowing through the magnetic circuit moreeffectively.

As described so far, according to the invention, it is possible toprovide the electromagnetically driven valve in which a sufficientlylarge amount of driving force can be obtained, and the control methodthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages thereof, technical and industrial significanceof this invention will be better understood by reading the followingdetailed description of preferred embodiments of the invention, whenconsidered in connection with the accompanying drawings, in which:

FIG. 1 illustrates a cross sectional view of an electromagneticallydriven valve according to a first embodiment of the invention;

FIG. 2 illustrates a perspective view of an electromagnet in FIG. 1;

FIG. 3 illustrates a perspective view of a lower disk (an upper disk) inFIG. 1;

FIG. 4 illustrates a schematic view of the upper disk and the lower diskthat have been oscillated as much as possible so that the valve isopened;

FIG. 5 illustrates a schematic view of the upper disk and the lower diskthat are oscillating toward the center position from the position atwhich the upper disk and the lower disk have been oscillated as much aspossible so that the valve is opened;

FIG. 6 illustrates a schematic view of the upper disk and the lower diskthat are at the center position;

FIG. 7 illustrates a schematic view of the upper disk and the lower diskthat have been oscillated as much as possible so that the valve isclosed;

FIG. 8 illustrates a schematic view of an electromagnetically drivenvalve according to a second embodiment of the invention; and

FIG. 9 illustrates a schematic view of an electromagnetically drivenvalve according to a third embodiment of the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In the following description and the accompanying drawings, theinvention will be described in more detail in terms of exemplaryembodiments. Note that, the same reference numerals will be assigned tothe same or equivalent components in the following description and theaccompanying drawings.

FIG. 1 illustrates a cross sectional view of an electromagneticallydriven valve according to a first embodiment of the invention. Theelectromagnetically driven valve according to the first embodiment formsan engine valve (an intake valve or an exhaust valve) of an internalcombustion engine such as a gasoline engine or a diesel engine. In thefirst embodiment, the description will be made concerning the case wherethe electromagnetically driven valve forms an intake valve. Note that,in the case where the electromagnetically driven valve forms an exhaustvalve, the same structure as that of the electromagnetically drivenvalve forming the intake valve is applied.

As shown in FIG. 1, an electromagnetically driven valve 10 is a rotarydriven type electromagnetically driven valve, and a parallel linkmechanism is applied to a motion mechanism thereof.

The electromagnetically driven valve 10 includes a drive valve 14 havinga stem 12 extending in one direction; a lower disk 20 and an upper disk30 which are connected to the stem 12 at different positions, and whichoscillates due to an electromagnetic force and an elastic force appliedthereto; an open/close electromagnet 60 which generates theelectromagnetic force (hereinafter, may be simply referred to as an“electromagnet 60”); a lower torsion bar 26 which is provided in thelower disk 20 and which applies the elastic force to the lower disk 20;and an upper torsion bar 36 which is provided in the upper disk 30 andwhich applies the elastic force to the upper disk 30. Permanent magnets71 and 72 are embedded in the electromagnet 60. The drive valve 14reciprocates in the direction in which the stem 12 extends (thedirection shown by an arrow 103) due to the oscillation motion of thelower disk 20 and the upper disk 30.

The drive valve 14 is provided in a cylinder head 41 in which an intakeport 17 is formed. A valve seat 42 is provided at a position at whichthe intake port 17 formed in the cylinder head 41 is communicated with acombustion chamber (not shown). The drive valve 14 further includes abell portion 13 formed at an end of the stem 12. As the drive valve 14reciprocates, the bell portion 13 alternately contacts the valve seat 42and moves away from the valve seat 42, whereby the intake port 17 isalternately closed and opened. Namely, when the stem 12 moves upward,the drive valve 14 is moved toward the valve closing position, and whenthe stem 12 moves downward, the drive valve 14 is moved toward the valveopening position.

The stem 12 is formed of a lower stem 12 m that extends from the bellportion 13, and an upper stem 12 n that is connected to the lower stem12 m with a lash adjuster 16 interposed between the lower stem 12 m andthe upper stem 12 n. The lash adjuster 16 serves a buffering memberlocated between the upper stem 12 n and the lower stem 12 m, and islikely to shrink and unlikely to stretch. The lash adjuster 16 absorbsan error in positioning of the drive valve 14 at the valve closingposition, and allows the bell portion 13 to reliably contact the valveseat 42. A connection pin 12 p, which protrude from the outer surface ofthe lower stem 12 m, is provided for the lower stem 12 m. A connectionpin 12 q, which protrudes from the outer surface of the upper stem 12 n,is provided for the upper stem 12 n at a predetermined distance from theconnection pin 12 p.

A valve guide 43 is provided in the cylinder head 41 so as to slidablyguide the lower stem 12 m in the axial direction. A stem guide 45 isprovided so as to slidably guide the upper stem 12 n in the axialdirection, at a position at a predetermined distance from the valveguide 43. The valve guide 43 and the stem guide 45 are made of metalmaterial such as stainless so as to endure sliding with the stem 12 at ahigh speed. A disk supporting base 51 is fitted on the top surface ofthe cylinder head 41, at a predetermined distance from the stem 12.

FIG. 2 illustrates a perspective view of the electromagnet 60 in FIG. 1.As shown in FIGS. 1 and 2, the electromagnet 60 is fitted to the disksupporting base 51, at a position between the lower disk 20 and theupper disk 30. The electromagnet 60 is formed of an open/close coil 62(hereinafter, may be simply referred to as a “coil 62”), and anopen/close core 61 (hereinafter, may be simply referred to as a “core61”) which has attraction surfaces 61 a and 61 b, and which is made ofmagnetic material. The core 61 has a shaft portion 61 p extending in thedirection perpendicular to the direction in which the stem 12 extends.The coil 62 is provided around the shaft portion 61 p, and formed of amono-coil (i.e., a coil formed of a piece of wire).

When an electric current is applied to the coil 62, a magnetic fluxflows between the core 61 and the lower disk 20, whereby a magneticcircuit 102 is formed. Similarly, when the electric current is appliedto the coil 62, a magnetic flux flows between the core 61 and the upperdisk 30, whereby a magnetic circuit 101 is formed. In the core 61, thepermanent magnet 71 is provided so as to be located on the magneticcircuit 101, and the permanent magnet 72 is provided so as to be locatedon the magnetic circuit 102. The core 61 is divided, by the permanentmagnets 71 and 72, into a portion 61 m including the shaft portion 61 p,and portions 61 n one of which faces the upper disk 30 and the other ofwhich faces the lower disk 20.

The permanent magnet 71 has the magnetic axis in the direction along themagnetic circuit 101. The south pole is formed in the side of thepermanent magnet 71, which is close to the portion 61 n. The north poleis formed in the side of the permanent magnet 71, which is close to theportion 61 m. With such a structure, the magnetic flux formed in thepermanent magnet 71 flows from the side close to the portion 61 n towardthe side close to the portion 61 m (in the direction shown by an arrow71 x) due to the magnetic poles. The permanent magnet 72 has themagnetic axis in the direction along the magnetic circuit 102. The northpole is formed in the side of the permanent magnet 72, which is close tothe portion 61 n. The south pole is formed in the side of the permanentmagnet 72, which is close to the portion 61 m. With such a structure,the magnetic flux formed in the permanent magnet 72 flows from the sideclose to the portion 61 m toward the side close to the portion 61 n (inthe direction shown by an arrow 72 x) due to magnetic poles.

The disk supporting base 51 is further provided with a valve openingpermanent magnet 55, and a valve closing permanent magnet 56 that isopposed to the valve opening permanent magnet 55 with the electromagnet60 interposed therebetween. The valve opening permanent magnet 55 has anattraction surface 55 a. A space in which the lower disk 20 oscillatesis defined between the attraction surface 55 a of the valve openingpermanent magnet 55 and the attraction surface 61 b of the electromagnet60. Similarly, the valve closing permanent magnet 56 has an attractionsurface 56 a. A space in which the upper disk 30 oscillates is definedbetween the attraction surface 56 a of the valve closing permanentmagnet 56 and the attraction surface 61 a of the electromagnet 60.

FIG. 3 illustrates a perspective view of the lower disk 20 (upper disk30) in FIG. 1. As shown in FIG. 1 and FIG. 3, the lower disk 20 has afirst end 22 and a second end 23, and extends from the second end 23toward the first end 22 in the direction that crosses the direction inwhich the stem 12 extends. The lower disk 20 is formed of an arm portion21 that has rectangular surfaces 21 a and 21 b and that extends from thesecond end 23 toward the first end 22, and a hollow cylindrical bearingportion 28 that is formed in the second end 23 side. The surface 21 afaces the attraction surface 61 b of the electromagnet 60, and thesurface 21 b faces the attraction surface 55 a of the valve openingpermanent magnet 55. The magnetic circuit 102 formed by applying anelectric current to the coil 62 forms a closed-loop that passes throughthe shaft portion 61 p of the core 61, the permanent magnet 72, and thearm portion 21.

A notched portion 29 is formed in the arm portion 21 in the first end 22side. A long hole 24 is formed in each of wall surfaces of the notchedportion 29, which face each other. In the second end 23 side, a centralaxis 25 is defined which extends in the direction perpendicular to thedirection from the first end 22 toward the second end 23. A through-hole27 extending along the central axis 25 is formed in the bearing portion28.

The upper disk 30 has the same shape as that of the lower disk 20. Inthe upper disk 30, a first end 32, a second end 33, an arm portion 31, asurface 31 b, a surface 31 a, a notched portion 39, and a long hole 34,a bearing portion 38, a through-hole 37, and a central axis 35 areformed, which correspond to the first end 22, the second end 23, the armportion 21, the surface 21 a, the surface 21 b, the notched portion 29,the long hole 24, the bearing portion 28, the through-hole 27, and thecentral axis 25 in the lower disk 20, respectively. The surface 31 afaces the attraction surface 61 a of the electromagnet 60, and thesurface 31 b faces the attraction surface 56 a of the valve closingpermanent magnet 56. The lower disk 20 and the upper disk 30 are made ofsoft magnetic material. The magnetic circuit 101 formed by applying anelectric current to the coil 62 forms a closed-loop that passes throughthe shaft portion 61 p of the core 61, the permanent magnet 71, and thearm portion 31.

The first end 22 of the lower disk 20 is movably connected to the lowerstem 12 m, when the connection pin 12 p is inserted into the long holes24. Similarly, the first end 32 of the upper disk 30 is movablyconnected to the upper stem 12 n, when the connection pin 12 q isinserted into the long holes 34. The second end 23 of the lower disk 20is movably supported by the disk supporting base 51 via the lowertorsion bar 26 inserted into the through-hole 27. Similarly, the secondend 33 of the upper disk 30 is movably supported by the disk supportingbase 51 via the upper torsion bar 36 inserted into the through-hole 37.With such a structure, the drive valve 14 can be reciprocated byoscillating the lower disk 20 with respect to the central axis 25, andthe upper disk 30 with respect to the central axis 35.

An elastic force is applied to the lower disk 20 by the lower torsionbar 26 in the clockwise direction around the central axis 25. An elasticforce is applied to the upper disk 30 by the upper torsion bar 36 in thecounterclockwise direction around the central axis 35. In the statewhere an electromagnetic force is not applied from the electromagnet 60,the lower disk 20 and the upper disk 30 are placed at the centerposition by the lower torsion bar 26 and the upper torsion bar 36. Thecenter position is the midpoint between the position at which the lowerdisk 20 and the upper disk 30 have been oscillated as much as possibleso that the valve is opened, and the position at which the lower disk 20and the upper disk 30 have been oscillated as much as possible so thatthe valve is closed.

FIG. 4 illustrates a schematic view of the upper disk 30 and the lowerdisk 20 that have been oscillated as much as possible so that the valveis opened. FIG. 5 illustrates a schematic view of the upper disk 30 andthe lower disk 20 that are moving toward the center position from theposition at which the upper disk 30 and the lower disk 20 have beenoscillated as much as possible so that the valve is opened. FIG. 6illustrates a schematic view of the upper disk 30 and the lower disk 20that are at the center position. FIG. 7 illustrates the upper disk 30and the lower disk 20 that have been oscillated as much as possible sothat the valve is closed. Next, the operation of the electromagneticallydriven valve 10 will be described in detail.

As shown in FIG. 4, when the drive valve 14 is at the valve openingposition, an electric current that flows around the shaft portion 61 pof the core 61 in a direction shown by an arrow 110 is applied to thecoil 62. Thus, the upper disk 30 is attracted to the attraction surface61 a of the electromagnet 60 due to an electromagnetic force generatedby the electromagnet 60. Meanwhile, the lower disk 20 is attracted tothe attraction surface 55 a by the valve opening permanent magnet 55. Asa result, the upper disk 30 and the lower disk 20 are oscillated as muchas possible so that the valve is opened and maintained in this state,against an elastic force of the lower torsion bar 26 provided around thecentral axis 25.

When the supply of electric current to the coil 62 is stopped, theelectromagnetic force generated by the electromagnet 60 disappears.Thus, the upper disk 30 and the lower disk 20 move away from theattraction surfaces 61 a and 55 a, respectively, and start to oscillatetoward the center position due to the elastic force of the lower torsionbar 26.

As shown in FIG. 5, an electric current is applied to the coil 62 in thedirection shown by an arrow 115, before the lower disk 20 and the upperdisk 30 reach the center position. Thus, a magnetic flux flows betweenthe core 61 and the lower disk 20 in the direction shown by an arrow117, and an electromagnetic force for attracting the lower disk 20 tothe attraction surface 61 b of the electromagnet 60 is generated. Also,a magnetic flux flows between the core 61 and the upper disk 30 in thedirection shown by an arrow 116, and an electromagnetic force forattracting the upper disk 30 to the attraction surface 61 a of theelectromagnet 60 is generated.

Since the direction in which the magnetic flux flows between the core 61and the lower disk 20 matches the direction in which the magnetic fluxformed in the permanent magnet 72 flows, the strength of magnetic fluxincreases. Accordingly, the electromagnetic force for attracting thelower disk 20 to the attraction surface 61 b increases. Meanwhile, sincethe direction in which the magnetic flux flows between the core 61 andthe upper disk 30 is opposite to the direction in which the magneticflux formed in the permanent magnet 71 flows, the magnetic flux flowingbetween the core 61 and the upper disk 30 and the magnetic flux formedin the permanent magnet 71 balance each other out, and, therefore, thestrength of magnetic flux is decreased. Accordingly, the electromagneticforce for attracting the upper disk 30 to the attraction surface 61 a isdecreased.

As described so far, providing the permanent magnets 71 and 72 makes itpossible to increases the electromagnetic force applied in the directionin which the lower disk 20 and the upper disk 30 oscillate, and todecrease the electromagnetic force applied in the direction opposite tothe direction in which the lower disk 20 and the upper disk 30oscillate. It is, therefore, possible to increase a force for closingthe drive valve 14 obtained due to the oscillation motion of the lowerdisk 20 and the upper disk 30.

As shown in FIG. 6, after reaching the center position, the lower disk20 and the upper disk 30 are oscillated from the center position towardthe position at which the lower disk 20 and the upper disk 30 are to beoscillated as much as possible so that the valve is closed, due to theelectromagnetic force of the electromagnet 60 for attracting the lowerdisk 20 to the attraction surface 61 b and the magnetic force of thevalve closing permanent magnet 56 for attracting the upper disk 30 tothe attraction surface 56 a. Providing the valve closing permanentmagnet 56 makes it possible to compensate for the shortfall of theelectromagnetic force, which is likely to occur particularly when thedrive valve 14 is near the valve closing position. It is, therefore,possible to prevent the force for closing the drive valve 14 fromdecreasing.

As shown in FIG. 7, when the lower disk 20 and the upper disk 30 haveoscillated as much as possible so that the valve is closed, the supplyof electric current to the coil 62 is stopped. Thus, the upper disk 30and the lower disk 20 move away from the attraction surfaces 56 a and 61b, respectively, and start to oscillate toward the center position againdue to the elastic force of the upper torsion bar 36.

As shown in FIG. 4, an electric current is applied to the coil 62 in thedirection shown by the arrow 110, before the lower disk 20 and the upperdisk 30 reach the center position. Thus, a magnetic flux flows betweenthe core 61 and the upper disk 30 in the direction shown by an arrow111, and an electromagnetic force for attracting the upper disk 30 tothe attraction surface 61 a of the electromagnet 60 is generated. Also,a magnetic flux flows between the core 61 and the lower disk 20 in thedirection shown by an arrow 112, and an electromagnetic force forattracting the lower disk 20 to the attraction surface 61 b of theelectromagnet 60 is generated.

At this time, since the direction in which the magnetic flux flowsbetween the core 61 and the upper disk 30 matches the direction in whichthe magnetic flux formed in the permanent magnet 71 flows, the strengthof magnetic flux increases. Accordingly, the electromagnetic force forattracting the upper disk 30 to the attraction surface 61 a increases.Meanwhile, since the direction in which the magnetic flux flows betweenthe core 61 and the lower disk 20 is opposite to the direction in whichthe magnetic flux formed in the permanent magnet 72 flows, the magneticflux flowing between the core 61 and the lower disk 20 and the magneticflux formed in the permanent magnet 72 balance each other out, and,therefore, the strength of magnetic flux is decreased. Accordingly, theelectromagnetic force for attracting the lower disk 20 to the attractionsurface 61 b is decreased. In this case as well, it is possible toincrease the electromagnetic force applied in the direction in which thelower disk 20 and the upper disk 30 oscillate, and to decrease theelectromagnetic force applied in the direction opposite to the directionin which the lower disk 20 and the upper disk 30 oscillate. It is,therefore, possible to increase the force for opening the drive valve14.

After reaching the center position, the lower disk 20 and the upper disk30 are oscillated from the center position toward the position at whichthe lower disk 20 and the upper disk 30 are to be oscillated as much aspossible so that the valve is opened due to the electromagnetic force ofthe electromagnet 60 for attracting the upper disk 30 to the attractionsurface 61 a and the magnetic force of the valve opening permanentmagnet 55 for attracting the lower disk 20 to the attraction surface 55a. In this case, providing the valve opening permanent magnet 55 makesit possible to prevent the force for opening the drive valve 14 fromdecreasing particularly when the drive valve 14 is near the valveopening position.

Then, the supply of the electric current to the open/close coil 62 isrepeatedly started and stopped at the above-mentioned timing. Thus, theupper disk 30 and the lower disk 20 are moved so as to be repeatedlyoscillated as much as possible so that the valve is opened andoscillated as much as possible so that the valve is closed. The drivevalve 14 are reciprocated due to this oscillation motion.

In the electromagnetically driven valve 10 according to the firstembodiment, when the lower disk 20 and the upper disk 30 areoscillating, the distance between the electromagnet 60 and the lowerdisk 20 decreases from the first end 22 toward the second end 23, andthe distance between the electromagnet 60 and the upper disk 30decreases from the first end 32 toward the second end 33. In contrast tothis, in the parallel driven type electromagnetically driven valve, theelectromagnet and the armature of the drive valve to which theelectromagnetic force is applied are uniformly apart from each otherwhile the distance therebetween uniformly changes. At a position atwhich the distance from the electromagnet is shorter, a larger amount ofelectromagnetic force is applied. Therefore, in the rotary driven typeelectromagnetically driven valve 10, a large amount of electromagneticforce can be applied to the drive valve 14, as compared with theparallel driven type electromagnetically driven valve.

Further, in the electromagnetically driven valve 10, the structure issuch that the lower disk 20 and the upper disk 30 are movably supportedby the disk supporting base 51 and the electromagnet 60 is providedbetween the lower disk 20 and the upper disk 30. Therefore, the heightof the electromagnetically driven valve 10 can be made low, as comparedwith the case where an electromagnet is provided above each disk andanother electromagnet is provided below each disk. In addition, withsuch a structure, just providing the electromagnet 60 formed of amono-coil makes it possible to oscillate the upper disk 30 and the lowerdisk 20, and to reciprocate the drive valve 14. As a result, the numberof the components of the electromagnet, which are expensive, can bereduced, resulting in a remarkable cost reduction.

In the first embodiment, in the process shown in FIG. 5, an electriccurrent is applied to the coil 62 before the lower disk 20 and the upperdisk 30 reach the center position. Note that, providing the permanentmagnets 71 and 72 makes it possible to supply the electric current atthis timing in the electromagnetically driven valve 10 using theelectromagnet 60 formed of a mono-coil. The reason will be described asfollows.

When the electromagnet 60 is formed of a mono-coil, the electromagneticforce generated by the electromagnet 60 is applied to the lower disk 20and the upper disk 30 in the same manner. Namely, in theelectromagnetically driven valve in which the permanent magnets 71 and72 are not provided, if an electric force is applied to theelectromagnet 60 when the lower disk 20 and the upper disk 30 are at thecenter position, as shown in FIG. 6, the lower disk 20 is attracted tothe attraction surface 61 b, and the upper disk 30 is also attracted tothe attraction surface 61 a with the same amount of force for attractingthe lower disk 20 to the attraction surface 61 b.

Accordingly, in order to oscillate the lower disk 20 and the upper disk30 against the elastic force of the lower torsion bar 26 and the uppertorsion bar 36 for attempting to maintain the lower disk 20 and theupper disk 30 at the center position, it is necessary to start thesupply of electric current to the coil 62 when the lower disk 20 and theupper disk 30 exceed the center position shown in FIG. 6. In this case,since the electromagnetic force acts more strongly between the lowerdisk 20 and the electromagnet 60, since the distance between the lowerdisk 20 and the electromagnet 60 is shorter than the distance betweenthe upper disk 30 and the electromagnet 60. Accordingly, the upper disk30 and the lower disk 20 can be oscillated as much as possible so thatthe valve is closed, as shown in FIG. 7.

As described above, however, providing the permanent magnets 71 and 72makes it possible to flexibly increase/decrease the electromagneticforce applied to the lower disk 20 and the upper disk 30. Accordingly,in the first embodiment, the time at which the supply of electriccurrent to the coil 62 is started can be set to a time before the lowerdisk 20 and the upper disk 30 reach the center position. As a result,the electromagnetic force generated by the electromagnet 60 can be moreeffectively applied to the lower disk 20 and the upper disk 30. It is,therefore, to increase the force for closing the drive valve 14 and theforce for opening the drive valve 14.

The electromagnetically driven valve 10 according to the firstembodiment of the invention includes the drive valve 14 having the stem12 serving as the valve stem; the lower disk 20 which serves as anoscillation member, which has the arm portion 21 made of magneticmaterial, and which extends from the first end 22 connected to the stem12 toward the second end 23 movably supported by the disk supportingbase 51 serving as a supporting member; the upper disk 30 which servesas an oscillation member, which has the arm portion 31 made of magneticmaterial, and which extends from the first end 32 connected to the stem12 toward the second end 33 movably supported by the disk supportingbase 51 serving as the supporting member; and the open/closeelectromagnet 60 serving as an electromagnet. The electromagnet 60includes the open/close core 61 serving as a core provided so as to facethe arm portions 21 and 31; and the open/close coil 62 serving as a coilprovided around the core 61. When an electric current is applied to thecoil 62, the electromagnet 60 forms the magnetic circuit 102 whichpasses through the core 61 and the arm portion 21, and the magneticcircuit 101 which passes through the core 61 and the arm portion 31.

The electromagnetically driven valve 10 further includes the permanentmagnet 72 that has the magnetic axis along the magnetic circuit 102 andthat is provided so as to act on the magnetic flux flowing through themagnetic circuit 102; and the permanent magnet 71 that has the magneticaxis along the magnetic circuit 101 and that is provided so as to act onthe magnetic flux flowing through the magnetic circuit 101. The lowerdisk 20 oscillates by using the second end 23 as a supporting point dueto the electromagnetic force applied from the electromagnet 60, and theupper disk 30 oscillates by using the second end 33 as a supportingpoint due to the electromagnetic force applied from the electromagnet60. The drive valve 14 reciprocates in the direction in which the stem12 extends due to the oscillation motion of the lower disk 20 and theupper disk 30 transmitted to the drive valve 14 via the first ends 22and 32, respectively.

The lower disk 20 and the upper disk 30, serving as the oscillationmembers, are provided in the direction in which the stem 12, serving asthe valve stem, extends, at a predetermined distance from each other.The electromagnet 60 is provided between the lower disk 20 and the upperdisk 30. The coil 62 is formed of a mono-coil.

The electromagnetically driven valve 10 further includes the valveopening permanent magnet 55 serving as a first permanent magnet providedso as to be opposed to the electromagnet 60 with the lower disk 20interposed therebetween; and the valve closing permanent magnet 56serving as a second permanent magnet provided so as to be opposed to theelectromagnet 60 with the upper disk 30 interposed therebetween.

A control method of the electromagnetically driven valve according tothe first embodiment of the invention is the control method of theabove-mentioned electromagnetically driven valve 10. The control methodincludes a step in which the lower disk 20 and the upper disk 30, whichhave been oscillated as much as possible so that the valve is opened,are started to oscillate toward the position at which the lower disk 20and the upper disk 30 are to be oscillated as much as possible so thatthe valve is closed, by stopping the supply of electric current to theelectromagnet 60; and a step which is performed after theabove-mentioned step, and in which the supply of electric current to theelectromagnet 60 is started before the lower disk 20 and the upper disk30 reach the center position that is the midpoint between the positionat which the lower disk 20 and the upper disk 30 have been oscillated asmuch as possible so that the valve is opened and the position at whichthe lower disk 20 and the upper disk 30 have been oscillated as much aspossible so that the valve is closed.

Also, the control method includes a step in which the lower disk 20 andthe upper disk 30, which have been oscillated as much as possible sothat the valve is closed, are started to oscillate toward the positionat which the lower disk 20 and the upper disk 30 are to be oscillated asmuch as possible so that the valve is opened, by stopping the supply ofelectric current to the electromagnet 60; and a step which is performedafter the above-mentioned step, and in which the supply of electriccurrent to the electromagnet 60 is started before the lower disk 20 andthe upper disk 30 reach the center position that is the midpoint betweenthe position at which the lower disk 20 and the upper disk 30 have beenoscillated as much as possible so that the valve is closed and theposition at which the lower disk 20 and the upper disk 30 have beenoscillated as much as possible so that the valve is opened.

In the first embodiment, the permanent magnets 71 and 72 are provided inthe core 61. However, the invention is not limited to this. Each of thepermanent magnets 71 and 72 may be provided at a position outside thecore 61, as long as the magnetic flux in the permanent magnet 71 formeddue to the magnetic poles acts on the magnetic flux flowing through themagnetic circuit 101, and the magnetic flux in the permanent magnet 72formed due to the magnetic poles acts on the magnetic flux flowingthrough the magnetic circuit 102. Also, the permanent magnet 71 may beprovided in the arm portion 31 of the upper disk 30, and the permanentmagnet 72 may be provided in the arm portion 21 of the lower disk 20.

With the thus configured electromagnetically driven valve 10 accordingto the first embodiment of the invention, providing the permanentmagnets 71 and 72 in the rotary driven type electromagnetically drivenvalve makes it possible to increase the force for opening the valve andthe force for closing the valve, and to obtain a sufficiently largeamount of driving force. It is, therefore, possible to improve theperformance of the engine including the electromagnetically driven valve10.

FIG. 8 illustrates a schematic view of an electromagnetically drivenvalve according to a second embodiment of the invention. Basically, theelectromagnetically driven valve according to the second embodiment hasthe same structure as that of the electromagnetically driven valve 10according to the first embodiment. Therefore, the description concerningthe portions having the same structure as those in the first embodimentwill not be made here.

As shown in FIG. 8, in the second embodiment, permanent magnets 81 and82 are provided in the electromagnet 60, instead of the permanentmagnets 71 and 72 in the first embodiment. Each of the permanent magnets81 and 82 is located so as to be adjacent to the shaft portion 61 p, andprovided between the core 61 and the coil 62. The permanent magnet 81 isprovided so as to face the upper disk 30, and the permanent magnet 82 isprovided so as to face the lower disk 20.

In the permanent magnet 81, the magnetic axis is formed along a magneticcircuit 118 formed between the core 61 and the upper disk 30, and themagnetic flux formed in the permanent magnet 81 due to the magneticpoles flows in the direction shown by an arrow 81 x. Similarly, in thepermanent magnet 82, the magnetic axis is formed along a magneticcircuit 119 formed between the core 61 and the lower disk 20, and themagnetic flux formed in the permanent magnet 82 due to the magneticpoles flows in the direction shown by an arrow 82 x that is opposite tothe direction shown by the arrow 81 x.

With such a structure, when an electric current is applied to the coil62 in the appropriate direction, the strength of magnetic flux flowingbetween the core 61 and the upper disk 30 is increased when the lowerdisk 20 and the upper disk 30 oscillate from the valve closing sidetoward the valve opening side, and is decreased when the lower disk 20and the upper disk 30 oscillate from the valve opening side toward thevalve closing side. Also, the strength of magnetic flux flowing betweenthe core 61 and the lower disk 20 is decreased when the lower disk 20and the upper disk 30 oscillate from the valve closing side toward thevalve opening side, and is increased when the lower disk 20 and theupper disk 30 oscillate from the valve opening side toward the valveclosing side.

With the thus configured electromagnetically driven valve according tothe second embodiment of the invention, the same effects as thosedisclosed in the first embodiment can be obtained. In addition, sincethe permanent magnets 81 and 82 are not embedded in the core 61, theelectromagnetically driven valve 60 can be easily produced at low cost.

FIG. 9 illustrates a cross sectional view of an electromagneticallydriven valve according to a third embodiment of the invention.Basically, the electromagnetically driven valve according to the thirdembodiment has the same structure as that of the electromagneticallydriven valve 10 according to the first embodiment. Therefore, thedescription concerning the portions having the same structure as thosein the first embodiment will not be made here.

As shown in FIG. 9, in the third embodiment, an electromagnet 90 isprovided instead of the electromagnet 60 in the first embodiment. Theelectromagnet 90 includes coils 94 and 95, and a core 93 that hasattraction surfaces 93 a and 93 b, and that is made of magneticmaterial. The core 93 has a shape obtained by combining a portion 91 anda portion 92 with each other, each of which has a cross sectional areahaving a substantially “E” shape. The portion 91 is positioned so as toface the upper disk 30, and has a shaft portion 91 p extending in thedirection in which the stem 12 extends. The portion 92 is positioned soas to face the lower disk 20, and has a shaft portion 92 p extending inthe direction in which the stem 12 extends. The coil 94 is provided soas to be around the shaft portion 91 p, and the coil 95 is provided soas to be around the shaft portion 92 p.

When an electric current is applied to the coil 94, a magnetic fluxflows between the portion 91 and the upper disk 30, whereby magneticcircuits 123 and 124 are formed in the core 93. When an electric currentis applied to the coil 95, a magnetic flux flows between the portion 92and the lower disk 20, whereby magnetic circuits 125 and 126 are formedin the core 93. Permanent magnets 97 and 98 are embedded in the core 93.The permanent magnet 97 has the magnetic axis along the magneticcircuits 123 and 125, and the magnetic flux formed in the permanentmagnet 97 due to the magnetic poles flows in the direction shown by anarrow 97 x. The permanent magnet 98 has the magnetic axis along themagnetic circuits 124 and 126, and the magnetic flux formed in themagnet due to the magnetic poles flows in the direction shown by anarrow 98 x that is opposite to the direction shown by the arrow 97 x.

With such a structure; when an electric current is supplied to each ofthe coils 94 and 95 in the appropriate direction, the strength ofmagnetic flux flowing between the core 93 and the upper disk 30increases when the lower disk 20 and the upper disk 30 oscillate fromthe valve closing side toward the valve opening side, and decreases whenthe lower disk 20 and the upper disk 30 oscillate from the valve openingside toward the valve closing side. Also, the strength of magnetic fluxflowing between the core 93 and the lower disk 20 decreases when thelower disk 20 and the upper disk 30 oscillate from the valve closingside toward the valve opening side, and increases when the lower disk 20and the upper disk 30 oscillate from the valve opening side toward thevalve closing side.

With the thus configured electromagnetically driven valve according tothe third embodiment of the invention, the same effects as thosedisclosed in the first embodiment can be obtained.

In the first to third embodiments, the description has been madeconcerning the case where the parallel link mechanism is applied to therotary driven type electromagnetically driven valve. However, theinvention is not limited to this. The invention can be applied to arotary driven type electromagnetically driven valve including a diskwhich is connected to the stem 12 at a first end and which is movablysupported by the disk supporting base 51 at a second end; and multipleelectromagnets which are provided above and below the disk and whichalternately apply an electromagnetic force to the disk.

Thus, the embodiment of the invention that has been disclosed in thespecification is to be considered in all respects as illustrative andnot restrictive. The technical scope of the invention is defined byclaims, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. An electromagnetically driven valve comprising: a drive valve thathas a valve stem and that reciprocates in a direction in which the valvestem extends, two oscillation members being formed of a firstoscillation member and a second oscillation member, which have an armportion made of magnetic material, and which extends from a first endthat is movably connected to the valve stem toward a second end that ismovably supported by a supporting member, respectively; an electromagnetwhich includes a core that is provided so as to face the arm portion,and a coil that is wound around the core, and which forms two magneticcircuits which pass through the core and the arm portions when anelectric current is applied to the coil for applying magnetism to thetwo oscillation members, respectively; and a permanent magnet which hasa magnetic axis along the magnetic circuits, and which is provided so asto act on a magnetic flux that flows through the magnetic circuits,wherein the permanent magnet is disposed so as to balance out themagnetic flux that flows through the magnetic circuit acting on one ofthe two oscillation members, and to increase the magnetic flux thatflows through the magnetic circuit acting on the other oscillationmember, the oscillation members is are oscillated by using the secondend as a supporting point due to an electromagnetic force applied fromthe electromagnet, and an oscillation motion of the oscillation membersis transmitted to the drive valve via the first end, whereby the drivevalve reciprocates in the direction in which the valve stem extends. 2.The electromagnetically driven valve according to claim 1, wherein thepermanent magnet is provided in the core.
 3. The electromagneticallydriven valve according to claim 1, wherein the permanent magnet isprovided between the core and the coil.
 4. The electromagneticallydriven valve according to claim 1, wherein the permanent magnet isembedded in the core, and the core is divided into two areas by theelectromagnet on the magnetic circuit.
 5. The electromagnetically drivenvalve according to claim 4, wherein the coil is formed of a first coilthat faces the arm portion of the first oscillation member, and a secondcoil that faces the arm portion of the second oscillation member.
 6. Acontrol method for an electromagnetically driven valve including a drivevalve that has a valve stem and that reciprocates in a direction inwhich the valve stem extends; two oscillation members being formed of afirst oscillation member and a second oscillation member, which aremovably connected to the valve stem; and an electromagnet that forms twomagnetic circuits between the electromagnet and the oscillation membersfor applying magnetism to the two oscillation members, respectively,wherein the permanent magnet is disposed so as to balance out themagnetic flux that flows through the magnetic circuit acting on one ofthe two oscillation members, and to increase the magnetic flux thatflows through the magnetic circuit acting on the other oscillationmember, the method comprising: a first step in which a supply of anelectric current to the electromagnet is stopped, whereby theoscillation members, which are at a first position at which theoscillation members have been oscillated as much as possible so that thedrive valve is moved in a first direction, are started to be oscillatedtoward a second position at which the oscillation members are to beoscillated as much as possible so that the drive valve is moved in asecond direction that is opposite to the first direction; and a secondstep which is performed after the first step is completed, and in whichthe supply of the electric current to the electromagnet is startedbefore the oscillation members reach a center position that is amidpoint between the first position and the second position.
 7. Thecontrol method for an electromagnetically driven valve according toclaim 6, wherein the first position is a position at which theoscillation members have been oscillated as much as possible so that thedrive valve is opened; and the second position is a position at whichthe oscillation members have been oscillated as much as possible so thatthe drive valve is closed.
 8. The control method for anelectromagnetically driven valve according to claim 6, wherein the firstposition is a position at which the oscillation members have beenoscillated as much as possible so that the drive valve is closed; andthe second position is a position at which the oscillation members havebeen oscillated as much as possible so that the drive valve is opened.